Air-inlet controller



Feb. 14, 1961 F. w. BARRY 2,971,329

AIR-INLET CONTROLLER Filed July 2o, 1959 7X 317% F/G. Z @AM/waff2,971,329 Patented Fels. i4, i961 nee ABl-INLET CONTRGLLER Frank W.Barry, Manchester, Conn., assigner to United Aircraft Corporation, EastHarord, Conn., a corporation of Delaware Files July zo, 1959, ser. No.'saaiss 12 claims. (ci. s0-35.6)

This invention relates to high-speed air inlets for aircraft and moreparticularly to means for sensing and controlling the position of thenormal shock within the inlet.-

Air-induction systems of turbojet or ramjet-propelled aircraft capableof high ysupersonic flight speeds are expeoted to require variablegeometry in order to achieve acceptable eiliciencies. The inlet woulduse variable geometry in order that the potential performance of theinduction system may be high throughout the spectrum of flightconditions anticipated. But, tln's potential performance can be realizedonly if the actual corrected air flow required by the engine equals theinlet corrected air llow corresponding to operation with this potentialperformance. Matching of the inlet air ilow to the engine air ow may beattained by adjusting the capture ow ofthe inlet or by spilling theexcess inlet air flow through a bypass, as illustrated herein. In thefollowing discussion, an embodiment of the invention utilizing avariable bypass is described.

One indication of the matching of engine and inlet corrected air flowsis the position of the normal shock in the inlet throat. lf the shock isdownstream ot the desired position, the engine corrected air ow, whichequalsthe net inlet corrected air flow (inlet corrected air ow less thebypass corrected air flow), is greater than the desired net inletcorrected air llow and the actual performance of the induction system isless than the potential. Reducing the bypass corrected air flow byclosing the bypass door would decrease the inlet corrected air llowtowards the desired value and would cause the shock to move upstreamtowards the desired shock position in the inlet throat which wouldprovide the desired potential inlet performance. TheV performance of theair-induction system would thus 'increase towards the desiredperformance.

n It is therefore an object of this invention to provide a supersonicair inlet for an airplane power plant or the like including means forsensing the position of the normal shock in the throat region of theinlet.

It is a further object of this invention to utilize a soundgeneratorwithin the inlet and a sensitive sound pickup upstream of thegenerator so that the exact location of the normal shock can beaccurately sensed. A signal commensurate with the'shock position is thenproduced, which signal is intended .to vary the flow characteristics inthe inlet.

It is a further object of this invention to provide a shock sensorin asupersonic inlet md provide a controlling signal which can vary theopening of a downstream bypass thereby accurately positioning the shock.

It is a still further ohjectof this invention to provide a shock sensorin a supersonic inlet and provide a controlling signal which can varythe inlet air ow thereby accurately positioning the shock.

lThese and other objects of this invention will become readily apparentfrom the following detailed description of 4the drawing in which:

Fig. l is a schematic cross section of an aircraft power plant inlet; g

`Fig. 2 is a schematic cross section of an enlarged portion of Fig. lshowing the shock position sensingand controlling system;

Fig. 3 is a schematic cross section illustrating a difierent position ofthe shock wave; and

Fig. 4 is a schematic cross section illustrating a variable area inletcontrol.

eferring to Fig. l, an air inlet is generally indicated at lil as havingan upstream opening l2, a convergent portion i4, a throat section lo anda divergent portion i8. The divergent portion ld exhausts to the inlet20 of a turbojet power plant or similar power plant generally indicatedat 22. Under conditions of high-speed fight, the inlet l2 will bereceiving flow at supersonic velocities and this llow will be shockeddown through a normal shock preferably located in the throat 16.Downstream of .the shock, the air Flow is subsonic for subsequentingestion in the engine. The flow characteristics within the inlet maybe regulated by a bypass 24, the opening of which is regulated by asuitable valve 2o. The valve 26 may be controlled by a servo motor 2d ina manner similar to that described in connection with Eig. 2.

Referring to 2, the throat lo is shown as having a shook wave 3@positioned adjacent the upstream end thereof. A sound generator Il@ isprovided at a point adjacent the downstream end of the throat lo and hasthe sound generated thereby directed in an upstream direction and aimedat a suitable pickup or microphone 42. The pickup fr?, has a shield df:-which prevents its accepting sounds emanating from a region upstreamthereof.

With the shock 3i? positioned as shown in Fig. 2, the pickup d2 cansense a substantially strong signal from the sound generator becauseboth the sound generator and the pickup 42) are located in the subsonicstream. On the other hand, if the s Loclr Sil is located as shown, forexample, in Fig. 3, the pickup i2 lies in a supersonic stream such thatthe sound waves from the generator will not reach `the pickup or elsethe signals sensed by the pickup are relatively weak.

Returning to Fig. 2, the pickup 42 has operative connections to anamplilier lo which is connected to an iron core 4b by means of a coildii. The spring loaded wiper 52 will be moved up and down to engagecontact strips S4 or 56, depending upon the relative strength of thesignal from the amplilier. Contact strip 54 is connected to a battery 58while wiper Se is connected to a battery 6i?. lt will be noted that thebatteries 58 and oil are so connected so that one will cause thereversible motor 62 to move in one direction while the other will causethe motor 62 to rotate in the opposite direction. The motor o2 isconnected by beveled gears 64 which will actuate a iaclzscrew 66 tothereby control the position of a bypass valve or door 63.

ln operation, if the shock moves toward a forward position, the soundsensed by the pickup or microphone 42 increases whereby the Wiper arm 52moves up and contacts the upper contact strip Sdand thus energizes themotor 62 in a direction to open the bypass door 6s and thereby increasethe bypass flow. As the shock moves in a downstream direction to a pointat or upstream o-f the pickup 42;, the sound sensed thereby decreases.rl`his causes the wiper 52 to contact strip 56 and eventually the bypassdoor is moved toward a closed position.

The wiper arm 5?, as well as the iron core 48 and the coil Sti maycomprise an ordinary AC. ammeter. Fig. 4 is a schematic illustrationshowing an inlet havving a variable capture area inlet operated by theshock sensing control to vary inlet air ilow. Thus, the inlet generallyindicated at 7G may have at least one movable wall pivoted at 73; Theposition of the wall '72 vbe controlled by the controller 7dwhich issimilar in operation to that shown in Fig. 2.

As a result of this invention it is apparent that a highly accurate butsimple system has been provided for sensing the position of the normalshock in a supersonic air inlet to accurately match the flow necessaryfor the power plant or similar device while obtaining optimum eticiencyfrom the inlet configuration.

Although one embodiment of this invention has been illustrated anddescribed herein, it will be apparent that various changes may be madein the construction and arrangement of the various parts withoutdeparting from the scope of the novel concept.

I claim:

1. In a flow control for a duct having supersonic uid lflow in at leasta portion of its length and having a portion therein where a shock wavemay be located, a sound generator in said duct located downstream of theshock for producing sound waves which travel in an upstream directiontoward the shock, a sound pickup in said duct adjacent the region wherethe shock is to be located for sensing the sound generated by said soundgenerator, and signal generating means connected to the said pickup forproducing a signal dependent upon whether the shock is upstream ordownstream of the pickup.

2. In a flow control for a duct having a supersoniq fluid flow in atleast a portion of its length and having a portion therein where a shockwave may be located, means for controlling a parameter of flow in saidduct, a sound generator in said duct located downstream of the shock forproducing sound waves which travel in an upstream direction toward theshock, a sound pickup in said duct adjacent the region where the shockis to be located for sensing the sound generated by said soundgenerator, signal producing means responsive to the sound sensing ofsaid pickup, and means responsive to said signal producing means foroperating said parameter controlling means to position the shock.

3.k In a control according to claim 2 including a servo deviceinterconnecting signal producing means and said means for operating saidparameter controlling means.

4. In a tlow control for a duct having supersonic iluid flow in at leasta portion of its length and having a portion therein where a shock wavemay be located, means located downstream of the shock for bleeding fluidfrom the duct, a signal generator in said duct located downstream of theshock for producing signals which travel in an upstream direction towardthe shock, the propagation of said signals being affected by said shock,pickup means in said duct adjacent the region where the shock is to belocated for sensing the signals from said signal generator, signalproducing means responsive to the signal sensing of said pickup means,and means responsive to said signal producing means for varying the flowthrough said bleeding means.

5. In a flow control according to claim 4 wherein said bleed includes avariable area orifice and said signal producing means includes acontroller for varying the area of said orifice.

6. In a control. for a duct haw'ng supersonic fluid flow in at least aportion of its length and having a portion therein Where a shock wavemay be located, means located downstream of the shock for bleeding fluidfrom the duct, a sound generator in said duct located downstream of theshock for producing sound waves which travel in any upstream directiontoward the shock, a microphone in said duct adjacent the region wherethe shock is to be located, said microphone facing in a downstreamdirection and being shielded from sounds emanating from upstreamthereof, electrical signal producing means responsive to the soundsensing of said microphone, and servo means responsive to said signalproducing means for varying the flow through said bleed- A ing means.

4located downstream of the shockfor bleeding fluid from the duct, asound generatorin said duct located down'- stream of the shock forproducing sound waves which travel in an Aupstream direction toward theshock, a sound pickup in said duct adjacent the region where the shockis to be located, said pickup facing in a downstream direction and beingshielded from sounds` emanating from upstream thereof, signal producingmeans responsive to the sound sensing of said pickup, and meansresponsive to said signal producing means for varying the flow throughsaid bleeding means.

8. In a ow control for a duct having supersonic uid flow in at least aportion of its length and having a portion therein where a shock wavemay be located, means for varying the inlet air flow, a signal generatorin said duct located downstream of the shock for producing signals whichtravel in an upstream direction toward the shock, the propagation ofsaid signal being affected by said shock, pickup means in said ductadjacent the region where the shock is to be located for sensing thesignals from said signal generator, signal producing means responsive tothe signal sensing of said pickup means, and means responsive to saidsignal producing means for controlling said inlet flow varying means.

9. In a flow control according to claim S wherein said inlet air flowvarying means includes a movable member and said signal producing meansincludes a controller for varying the position of said member.

10. In a control fora duct having supersonic uid flow in at least aportion of its length and having la portion therein where a shock wavemay be located, means for regulating the inlet air flow, a soundgenerator in said duct located downstream of the shock for producingsound waves which travel in an upstream direction toward the shock, amicrophone in said duct adjacent the region where the shock is to belocated, said microphone facing in a downstream direction and beingshielded from sounds emanating from upstream thereof, electrical signalproducing means responsive to the sound sensing of said microphone, andservo means responsive to said signal producing means for controllingsaid regulating means.

ll. In a control for an air inlet duct having supersonic fluid flow inat least a portion of its length and having a portion therein where ashock wave may be located, means for regulating the inlet air fiow, asound generator in said duct located downstream of the shock forproducing sound waves which travel in lan upstream direction toward theshock, a sound pickup in said duct adjacent the region where the shockis to be located, said pickup facing in a downstream direction and beingshielded from sounds emanating from upstream thereof, signal producingmeans responsive to the sound sensing of said pickup, and meansresponsive to said signal producing means for controlling saidregulating means.

12. In a-control for a duct having supersonic fluid flow in at least aportion of its length and having a region therein wherein a shock wavemay be located, means for varying a parameter of flow in the duct, asignal generator in a downstream subsonic region of flow in said ductfor generating a signal traveling upstream toward the shock, thepropagation of said signal being affected by said shock, means in thevicinity of the shock for receiving the signals from said signalgenerator, means generating a control signal in response to the signalreceived by said receiving means, and means responsive to said controlsignal for varying said parameter varying means.

References Cited in the file of this patent UNITED STATES PATENTS WolffFeb. 24, 1942 Sziklas Dec. l, 1959 OTHER REFERENCES York 6, N.Y.

